AZ St Jan Brugge Oostende, campus Oostende
Cardiac troponin I (cTnI) levels rise within 3–6 hours after onset of symptoms, peak at 18–24 hours, and persist for 4–7 days. Implementation of high sensitivity troponin I (hs‑TnI) assays helps to detect very low troponin levels, making it easier to detect myocardial infarction (MI) and acute coronary syndrome (ACS) earlier. The objective of this research is to validate hs‑TnI on the Vitros 5600 device and to apply 0/1‑hour algorithm to detect MI or ACS.
Standard troponin I and hs‑TnI are determined according to the principle of immunometric technique (sandwich) on microwell technology of Vitros 5600 device with serum samples of patients received by the lab. For the validation method of hs‑TnI, repeatability and reproducibility were determined from Liquicheck cardiac markers plus control LT level 2 and level 6 of Biorad, Vitros immundiagnostic hs‑TnI low control of Ortho Clinical Diagnostics, Cliniqa controls and two patient samples. Bias was determined with the help of hs‑TnI calibrator. The control test of normal range was also performed.
The CV values obtained from the level 2 and level 6 of Biorad and Ortho Clinical Diagnostics for both repeatability and reproducibility were considered as acceptable according to the biological variation value but not according to the value recommended by ‘Instructions for use’ of hs‑TnI. However, the two positive patient samples and the Cliniqa controls meet the acceptable CV range of the biological variation value and the value recommended by ‘Instructions for use’ of hs‑TnI. Determination of bias meets the acceptable range of biological variation value. Control test of normal range also meets the requirement for using the normal range of hs‑TnI provided by the ‘Instructions for use’.
The testing and validation study included 40 patients, respectively, of which 20 positive and 20 negative standard troponin I tests were monitored. For the comparison between the two parameters, only the correspondence between the results is considered. The negative standard troponine I test results completely corresponds to the results of hs‑TnI test. However, two divergent results emerged during the comparison of the positive standard troponine I test with hs‑TnI test. If 0/1‑hour algorithm was to be applied, these patients would meet the requirement of ‘rule-in’ criteria.
The hs‑TnI measurement meets the two criteria recommended for high‑sensitive cardiac troponin assay. The total imprecision (expressed as CV %) at the 99th percentile value should be ≤10 % and the measurable concentrations below the 99th percentile upper reference limit should be at a concentration value above the assay Limit of Detection for at least 50 % of adult healthy population. Standard troponin I test cannot detect a negative value under 0.012 ng/mL (12 ng/L) whereas hs‑TnI test can detect a negative value from 1.5 ng/L.
According to the results, the test can be implemented for ‘rule-in’ criteria of 0/1‑hour algorithm.
MRSA is a major cause of infections. Therefore, a MRSA screening is performed daily at the hospital.
MRSA screening agar plates are used to detect MRSA. The purpose of this study is to compare the MRSA select II (Biorad) and Brilliance MRSA 2 (Oxoid) screening agar plates based on color colonies, the interference of the wiper fluid on the plates and the detection limit, specificity, sensitivity, PPW and NPW are determined.
The chromogenic agar are used to detect the presence of MRSA. In suspect colonies, further identification with the MALDI-TOF MS, VITEK 2 Compact, PBP2a Culture Colony test and / or cefoxitin E-test is performed.
All MRSA samples were positive on both plates. All MSSA samples were negative at MRSA select II (Biorad). Eighteen of the Twenty were negative at Brilliance MRSA 2 (Oxoid).
On the other two plates suspicious colonies were visible. Further identification was performed and both were identified as MSSA. In the CNS samples, both plates were negative. This is as expected. At the wipers, more false positive results were observed with Brilliance MRSA 2 (Oxoid) than in MRSA select II (Biorad). Also, there were significantly more plates of Brilliance MRSA 2 (Oxoid) that were affected by the wiper. The detection limit is very good at Brilliance MRSA 2 (Oxoid) because, according to this research, it is better than what the company had specified. The sensitivity and negative predictive value were 100% for both MRSA screening agar plates and therefore very good. The specificity and positive predictive value were better at MRSA select II (Biorad). This may be due to lack of experience of interpreting the plates.
MRSA select II (Biorad) is currently being used. Due to the lack of experience, the Brilliance MRSA 2 (Oxoid) plates are less interpretable. The laboratory of the hospital AZ-Sint-Jan-Bruges-Ostend AV campus Henri Serruys is strongly considering using the Brilliance MRSA 2 (Oxoid) plate as the plate is cheaper and to improve uniformity in the fusion hospital.
The purpose of this study is evaluating Cobas e411 and VIDAS in order to be able to use the best device in the laboratory. These devices are able to measure two parameters of thyroid autoantibodies, particularly anti-thyroid peroxidase (anti-TPO) and anti-thyroglobulin (anti-TG).
In some people, there are antibodies present in the blood which are directed against the thyroid. This is done by a mistake of the immune system that will attack its own cells. It sees these cells as enemy invaders. The determination of thyroid antibodies has a place in the differential diagnosis of thyroid disorders.
The Cobas e411 uses the technology of electrochemiluminescence immunoassay (ECLIA). The test principle of anti-TPO and anti-TG is based on a competition reaction. The VIDAS uses the technology of an enzyme linked fluorescent assay, based on the assay principle of a two-step sandwich ELISA technique for both anti-TPO and anti-TG.
The two devices are compared by checking the repeatability and reproducibility. A method comparison is done between the Cobas e411 and the Cobas e602 of campus Sint-Jan by using a Passing-Bablok regression analysis. Because of different reference ranges, the method comparison of the VIDAS and Cobas e602 is based on the agreement of results.
The results of the repeatability and reproducibility of anti-TPO on the Cobas e411 and the VIDAS are acceptable. The repeatability results of anti-TG on the Cobas e411 are acceptable, the VIDAS results are less acceptable only for the negative control. The reproducibility results of anti-TG on the Cobas e411 are not acceptable, the results of the VIDAS are only for the negative control LTA not acceptable.
The results of method comparison of the Cobas e411 and the Cobas e602 are acceptable. The results of method agreement between the Cobas e602 and VIDAS show discordant cases for anti-TG, where the VIDAS gives the right results.
Of cause of the results of this study and the low request for both tests, the laboratory of campus Henri Serruys gives the preference to analyse anti-TPO and anti-TG on the platform of VIDAS.
- Accuracy – correlation study
- Controls: operator-targets-contamination
- Impact of different kinds of culture media
- Age of the cultures
- Validation of the toothpicks
Dr. S. Van Erum
Dr. Evelyne Vanderstraeten